IX. THE REJUVENATION OF VIRUSES 197 



lieve that some soil-inhabiting organism acts as a vector, presumably 

 a nematode (39) 



Furthermore, it may be possible that some animal viruses multi- 

 ply in certain bacterial cells to establish rejuvenation and subsequently 

 to infect again the animals. If so, the bacteria would be thought 

 pathogenic. The majority of workers believe that the causative 

 agent of whooping cough is a kind of bacteria, whereas some others 

 claim it to be a virus ; the infection was reported actually possible 

 through the filtrates of the patient excretes. 



Again, scarlet fever is usually believed to be caused by strepto- 

 coccus but repeatedly a virus has been suspected. Bringel (106) has 

 claimed to have succeeded in isolating a filtrable agent which makes 

 a strain of haemolytic streptococcus capable of causing scarlet fever. 

 This agent when present in the filtrate is so unstable as to be inacti- 

 vated by heating to about 60°C. for 45 min. 



If a virus causes a venereal disease, it can be rejuvenated by 

 being transmitted from one sex- to the other. Such a rejuvenation may 

 be as complete as that brought about by sexual reproduction, since 

 the virus is always to be transmitted in turn between both sexes. It 

 is known that the virus of lymphogranuloma venereum, a highly 

 advanced virus causing a venereal disease, fails to leave any immunity 

 in the host in spite of its highly fixed character. For achieving the 

 rejuvenation, the establishment of the immunity must be unfavourable 

 for such a virus, so that the character not to leave the virus pattern 

 which can contribute to the immunity might develop, the individuals 

 having this character being selected as the fittest. Such a virus 

 might evolve into bacteria, such as gonococcus, w-hich have also the 

 character to cause no immunity. 



